The goal of this project is to evaluate the chronic toxicity and carcinogenicity of sodium tungstate dihydrate (STD) in rats and mice exposed via exposure in drinking water. Tungsten is a high production volume metal that is used in a variety of commercial applications, including military applications as a replacement for lead in small caliber ammunition and as a substitute for depleted uranium in armor penetrators. In addition, tungsten is found in dietary supplements and has potential clinical use as an antidiabetic therapy. 2-Year chronic toxicity and carcinogenicity studies of STD are in the in life phase. Keywords: toxicity, carcinogenicity, drinking water, sodium tungstate dehydrate